Study indicates warmest summer in at least 500 years

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WASHINGTON — The killing summer of 2003, when there were more than 19,000 deaths attributed to the heat, may have been the hottest in Europe in 500 years, according to an analysis of temperatures dating back to 1500.

“When you consider Europe as a whole, it was by far the hottest,” said Jurg Luterbacher, climatologist and the first author of a study appearing this week in the journal Science.

Luterbacher, a researcher at the University of Bern, Switzerland, said increased temperatures were not limited to summer in Europe. Winters also have been warmer than the historical record.

He said the study found that the average winter and annual temperatures were the highest in 500 years in the three decades from 1973 to 2002.

Human influence not studied
Luterbacher said other studies have linked the rising average temperatures to global warming caused the burning of fossil fuels, but his team did not attempt to make such a connection.

“We don’t make any analysis of the human influence,” he said. “We don’t attempt to determine the cause. We only report what we find.”

Other climatologists, however, say the new study agrees with models that have predicted a steady rise in global temperature as the result of greenhouse gases released into the atmosphere from the burning of fossil fuels and other sources.

Stephen Schneider, a climate expert at Stanford University and a prominent advocate for human-caused global warming, said the Luterbacher paper is consistent with what climate modelers have been predicting for 20 years.

“The data is starting to line up showing that those projections were correct,” Schneider said. “We warned the world that this was likely to happen because we believed the theory, but couldn’t actually prove it was happening. Now the data is coming in saying it is ... getting clearer and clearer. This paper is yet another ... saying that.”

Hot, cold cyclesIn the study, Luterbacher and his team analyzed the temperature history of Europe starting in 1500 to the present. For the earliest part of the half millennium, the temperatures are estimates based on proxy measures, such as tree rings and soil cores. But after about 1750, he said, actually instrumented readings became generally available throughout Europe.

During the 500 years, there were trends both toward cool and toward hot. The second hottest summer in the period was in 1757. That was followed by a cooling trend that continued until early in the 20th century. The summer of 1902, for instance, was the coolest of the entire record.

Starting in 1977, the record shows “an exceptionally strong, unprecedented warming,” the researchers report, with average temperatures rising at the rate of about 0.36 degrees per decade.

Then came last summer.

“The summer of 2003 exceeded 1901 to 1995 European summer temperatures by around 2 degrees C (3.6 degrees F),” the study said. “Taking into account the uncertainties (in the study method), it appears that the summer of 2003 was very likely warmer than any other summer back to 1500.”

Record temperatures were recorded in most of the major cities of Europe last summer, with many readings over 100 degrees. Authorities have attributed thousands of deaths to the excess heat, making the heat wave one of the deadliest weather phenomena in the past century.

The summer's legacy
In France, the toll was estimated at about 14,802 dead. About 2,000 more than normal died in August in England and Wales. On Aug. 11, Britain’s hottest day on record, there were 363 more deaths than average and the temperature reading reached 101.3 in Brogdale in southeastern England.

Altogether in Europe, based on official numbers collected by The Associated Press, there were more than 19,000 excess deaths in the summer months. France was hardest hit, but the average number of summer deaths increased by 4,175 in Italy, 1,300 in Portugal and more than 1,000 in the Netherlands.

The intense heat also wilted crops, caused wildfires and continued a centurylong trend of melting the continent’s glaciers.

Luterbacher said some mountain glaciers have shrunk by 50 percent in the past century in Europe, and some ice fields lost 10 percent of their mass last summer alone.

In addition, he said, the long trend of warming temperatures is now melting the high altitude permafrost — the soil that usually remains frozen year-round — and that buildings, bridges and roadways are now threatened with unstable foundations.

And it may get worse, said Luterbacher. He said some studies forecast that if the warming trend continues, Europe may have summers like 2003 every other year starting late in this century.